On April 15, 1947, at Ebbets Field in Brooklyn, N.Y., Jack Roosevelt Robinson, at the age of 28, became the first African American to play for a major-league baseball team since the 1884 season, when Moses Fleetwood "Fleet" Walker played for the Toledo Blue Stockings between May 1 and Sept. 4. (William White, a student at Brown, played one game for the Providence Grays of the National League in 1879, hence technically breaking the color barrier.) Before a crowd of 26,623 spectators (of whom approximately 14,000 are thought to have been black), though he got no hits, Robinson scored a run to contribute to the Dodgers' 5-3 victory over the Boston Braves.

The rest, as they say, is history: During a relatively short career spanning only nine years, Robinson was Rookie of the Year in 1947, Most Valuable Player in 1949, took his team to the World Series six times (including one World Championship in 1955) and made the All-Star Team six times. He was inducted into the Hall of Fame in 1962, and in an unprecedented gesture to his enormous historical significance and prowess as an athlete, Major League Baseball retired his number "42" in 1997, the first time this has been done for any athlete in any sport.

These are the facts of his baseball career, which kids my age knew by heart. But what virtually none of us knew back then, and many people don't know today, is that Lt. Jack Roosevelt Robinson was actually court-martialed in 1944! Court-martials are military courts, usually consisting of a panel of commissioned officers who conduct a criminal trial. There are three types of courts-martial: Summary Court-Martial, Special Court-Martial and General Court-Martial. Robinson faced a General Court-Martial.

Had he been found guilty, the whole course of black participation in professional baseball and every other professional sport, as well as the modern civil rights movement, most probably would have been profoundly affected adversely. But the circumstances of that court-martial only add to Robinson's credentials as one of the true pioneers of the civil rights movement.

Standing his Ground

As detailed in the masterful Jackie Robinson: A Biographyby Arnold Rampersad, on July 6, 1944, Robinson "became entangled in a dispute that threatened to end his military service in disgrace." While riding on a military bus returning to a hospital from "the colored officers club," Robinson sat next to Virginia Jones, the wife of one of his fellow officers. Jones looked white -- at least the white bus driver thought so. After a few blocks, the driver abruptly ordered Robinson "to move to the back of the bus." Robinson, justifiably outraged, refused. Among other things, he had read that segregation was no longer allowed on military buses(pdf) and proceeded to engage in a form of protest prefiguring a similar action by Rosa Parks 11 years later.

Rampersad reprints Robinson's statement about what happened next: "The bus driver asked me for my identification card. I refused to give it to him. He then went to the Dispatcher and told him something. What he told him I don't know. He then comes back and tells the people that this nigger is making trouble. I told the driver to stop f---in with me, so he gets the rest of the men around there and starts blowing his top and someone calls the MP's." Robinson was placed under "arrest in quarters," which meant that "he would be considered under arrest at the hospital, although without a guard. Robinson was then taken to the hospital in a police pickup truck." A white officer would recall that Robinson "was handcuffed, and there were shackles on his legs. Robinson's face was angry, the muscles on his face tight, his eyes half closed."

Robinson was transferred to the 758th Tank Battalion on July 24, "where the commander signed orders to prosecute him." On that day, he was arrested. Rampersad says that "At 1:45 in the afternoon on August 2, the case of The United States v. 2nd Lieutenant Jack R. Robinson, 0-10315861, Cavalry, Company C, 758th Tank Battalion, began." Robinson's fate was in the hands of nine men, eight of them white: "One was black; another had been a UCLA student [where Robinson had been an undergraduate]. Six votes were needed for conviction."

Robinson faced two charges: "The first, a violation of Article of War No. 63, accused him of 'behaving with disrespect toward Capt. Gerald M. Bear, CMP, his superior officer' … The second charge was a violation of Article No. 64, in this case 'willful disobedience of lawful command of Gerald M. Bear, CMP, his superior.' " Three other charges were dropped before the trial began. Testimony reveals how bravely Robinson had fought to defend himself on the evening of the incident, including reportedly saying quite heroically, "Look here, you son-of-a-bitch, don't you call me no nigger!" After a four-hour trial, Robinson was exonerated: "Robinson secured at least the four votes (secret and written) needed for his acquittal. He was found 'not guilty of all specifications and charges.' "

Setting History in Motion

As the philosopher Cornel West put it in his introduction to Jackie Robinson's autobiography, I Never Had It Made, "More even than either Abraham Lincoln and the Civil War, or Martin Luther King, Jr. and the Civil Rights movement, Jackie Robinson graphically symbolized and personified the challenge to a vicious legacy and ideology of white supremacy in American history," a challenge, Cornel continued, that "remains incomplete, unfinished."

It is so easy for us to underestimate the enormous significance, both symbolically and politically, of Jackie Robinson's integration of Major League Baseball, today when so very many black athletes play such dominant roles in sports. Baseball was America's "national pastime," and it was also, accordingly, the ultimate bastion of white male dominance. If professional sports as a whole were to be desegregated -- and to some extent, the larger society -- this effort had to commence on the baseball field. To understand the even broader social and political import of what Robinson's actions on the field initiated, we need only consider the chain reaction of crucial episodes in the history of the civil rights movement that unfolded almost immediately after his first season with the Dodgers.

First, President Harry Truman issued Executive Order 9982 on July 26, 1948, just over a year after Robinson faced his first pitcher at Ebbets Field, abolishing racial discrimination in the armed forces. It is certainly reasonable to assume that Truman's timing was informed by Robinson's successful integration of professional baseball. Truman's desegregation of the military no doubt informed the Supreme Court's Brown v. Board decision desegregating public schools in 1954, which in turn informed the actions of Rosa Parks on her bus, leading to the Montgomery Bus Boycott. Out of the Montgomery Bus Boycott emerged the leadership role of the young Martin Luther King Jr. Without Martin Luther King, Jr. there would have been no modern civil rights movement.

And without the civil rights movement, there would have been no affirmative action, and without affirmative action, to fast-forward a bit, there would be no Barack Obama.

I'm not claiming that what Jackie Robinson alone achieved in 1947 set off this chain reaction of events, but his courage and bravery played a major role in the history of integration, both on the field and throughout American society, and no history of the civil rights movement would be complete without noting Robinson's major role, and according him a place of honor and immortality in African-American history because of it.

Off the field, Jackie Robinson was also one of movement's strongest voices, in spite of the fact that he had to withstand so much abuse on the field and from the stands in stoic yet eloquent silence. He once wrote, in a letter to Averell Harriman in 1955, that "We are sure that in time, the spirit embedded in the Constitution of the United States will prevail in all sections of the country; however, it is important now that we be vigilant in guarding against flagrant miscarriages of justice that will hurt not only the innocent victims, but also the perpetrators." He desperately -- and unsuccessfully -- lobbied Republican presidential candidate Richard Nixon to intervene when Dr. King was jailed in Georgia in October 1960. Some scholars believe that John Kennedy's decision to do so led to his margin of victory over Nixon.

Jackie Robinson was a "race man," as they said in those days, dedicated to the betterment of the black people. As he wrote in another letter to William Keefe in 1956, "I speak to you only as an American who happens to be an American Negro and one who is proud of that heritage. We ask for nothing special. We ask only that we be permitted to compete on an even basis, and if we are not worthy, then the competition shall, per se, eliminate us." Hank Aaron noted this quite eloquently in his introduction to I Never Had It Made: "Jackie Robinson gave all of us -- not only black athletes but every black person in this country -- a sense of our own strength." As the conservative columnist George Will correctly noted, Robinson's life is "One of the great achievements not only in the annals of sports, but of the human drama anywhere, anytime."

It is for these reasons that we should all be grateful that Robinson was acquitted at his court-martial for refusing to move to the back of the bus, and that we should honor the immortal legacy of Jackie Robinson as one of the greatest heroes of the modern civil rights movement, this extraordinarily noble man who suffered so much in so many ways for the sacrifices he made, both publicly and privately, so that African Americans could continue their long march for freedom and equality in this great republic with new vigor and determination.

Henry Louis Gates Jr. is the Alphonse Fletcher University Professor and the director of the W.E.B. Du Bois Institute for African and African-American Research at Harvard University. He is also the editor-in-chief of The Root. Follow him on Twitter.